/**
 * @param {character[]} s
 * @return {void} Do not return anything, modify s in-place instead.
 */
var reverseString = function(s) {
  var len = s.length-1;
  s.find((x,index)=>{
      if(index<=len/2<<0){   //取一半反转
          [s[len-index],s[index]] = [s[index],s[len-index]] 
      }
  }) 
  return s
};

reverseString(["h","e","l","l","o"]);